1. Field of the Invention
The present invention relates to a semiconductor laser device, used as a light source for an optical disc, such as DVD or the like. More particularly the present invention relates to a semiconductor laser device having a photodetector for detecting light.
2. Discussion of the Related Art
In a semiconductor laser device as shown in FIG. 11, fluctuation of light is detected by installing a photodiode 2 in the device which receives a laser beam emitted from the monitor side of the end face of the light guide of a semiconductor laser element 1 and activates an APC (Automatic Power Control), thereby maintaining a constant output power of light.
For example, Japanese Unexamined Patent Publication No. S59-208886 discloses a structure of a light emitting semiconductor device, wherein a laser beam from a semiconductor laser chip is emitted from the resonator end faces formed on the top and bottom of the chip, and a light receiving element is fixed on a stem with an angle for monitoring the laser beam emitted from the mirror face at the bottom of the chip, whereby preventing light reflected on the surface of the light receiving element from going out of the device through the transparent window of the cap.
In addition, Japanese Unexamined Patent Publication No. S63-317931 discloses an optical head having a beam splitter 10 as shown in FIG. 12, which splits a laser beam into a reflecting laser beam and a transmitting laser beam, installed at a predetermined angle to the optical axis of the laser beam.
Also, Japanese Unexamined Patent Publication No. S60-39880 discloses a light emitting device as shown in FIG. 13, which includes a laser chip emitting laser beams from its both end faces; a portion of the laser beams is transmitted through a transparent window and emitted out from a package consisting of a stem and a cap, another part of the laser beam is emitted toward a photodetector mounted on the main surface of the stem; a photodetector 2 is placed on the stem at an angle, and an antireflection film 11 comprising black paint or the like is coated on the inner wall of the cap 6 and the main surface of the stem 4, respectively, so as to prevent light reflected from the surface of the photodetector from being emitted out of the transparent window.